Shapes can be combined and separated (composed and decomposed) to make new shapes.

Opportunities to combine, rotate, and compare shapes will help children develop understanding of part-whole relationships within and among shapes (as when two identical right triangles are combined to make a rectangle).

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This child successfully attempts to match geo-solids using triangular prism-shaped blocks. Focus on the Child videos are taken from one-on-one interviews with individual children. The interviews are designed to elicit evidence of children’s mathematical thinking. They are not teaching episodes or formal assessments.

Instructor Lisa Ginet explains how to make tangram puzzles, an ancient Chinese game made from seven shapes cut from a square. Over 6500 different arrangements can be made from these seven simple shapes!